1. Field of the Invention
The invention relates to a lens array element and an image display device, and particularly relates to a lens array element electrically controlling generation of a lens effect for achieving three-dimensional display, and an image display device using the lens array element.
2. Description of Related Art
A method of achieving stereoscopy has been known in the past, where a parallax image causing parallax between both eyes of a viewer is shown for stereoscopy, which includes a method where a viewer needs to use special glasses for achieving stereoscopy, and a method where a viewer need not use the glasses.
The method needing the glasses is used, for example, for a projector in a movie theater or a television image receiver. The method needing no special glasses is expected to be used for a television image receiver, and a display of a portable electronic-instrument such as a mobile phone, a smartphone, or a netbook computer.
A specific way of achieving the method needing no special glasses may include an optical device for three-dimensional display assembled on a screen of a two-dimensional display device such as liquid crystal display, the optical device deflecting display image light from the two-dimensional display device to multiple view angle directions.
The optical device for three-dimensional display includes a lens array having a plurality of cylindrical lenses arranged in parallel, as well known. For example, in the case of binocular stereoscopy, different parallax images are shown to both eyes of a viewer, thereby the viewer senses a stereoscopic effect. To achieve this, a plurality of cylindrical lenses extending in a vertical direction are arranged in parallel in a horizontal direction with respect to a display surface of a two-dimensional display device, so that display image light from the two-dimensional display device is deflected in the horizontal direction, and thus horizontal parallax images appropriately arrive at both eyes of a viewer.
In addition to the cylindrical lenses, a changeable lens array element using liquid crystal lenses has been known (hereinafter, called liquid-crystal lens array element) is known (for example, see Japanese Unexamined Patent Application Publication No. 2008-9370).
The liquid-crystal lens array element may electrically switch between presence and absence of a lens effect similar to that of the cylindrical lenses. Therefore, the liquid-crystal lens array element is provided on a screen of a two-dimensional display device, enabling switching between two display modes, a two-dimensional display mode due to a no-lens-effect state and a three-dimensional display mode due to a lens-effect state.